Why Too Much Light Can Be Harmful to Zooxanthellae

[JCOLE]

@Dana Riddle thank you for this! I am wondering this myself. I recently purchased a Seneye Reef PAR meter and it is giving readings around 1500+ at the top of the rocks and around 500+ at the sand bed. Seems very high. However, I run 4 black boxes at 100% both channels with 2 80w Blue+ T5s. I am getting decent growth and coloring but wondering if I am stunting the growth. I have an acro dominate tank and nothing has bleached as of yet. Do you think it is possible that the PAR meter is correct?

Also, I am curious how do you know when photochemical quenching is happening and photosynthesis has shut down?

 

[User1]

DLI is 'Daily Light Integral'. The best analogy is this - PAR is reported as Photosynthetic Photon Flux Density (PPFD) in micromol/m2/sec. If this were rainfall, it would be rain drops per square meter per second. Have you ever heard a weather report stating drops per second? Of course not, we're interested in the *total rainfall* (usually inches per event) and that's what DLI is. It reports the total number of photons in the photoperiod (and reported as mol/m2/photoperiod.) I measured DLIs in Hawaii and saw it could be as high as 30 mol/m2/photoperiod. The DLI in my reef is 7.

You probably have one, or I missed it (probably the case), but is there an article that guilds a hobbyist say with a seneye to calculate this? I see micromol/m2/sec as a formula but not sure what it is or if it is something at hobbyists level person can calculate. Or if it is even worth knowing.

Thanks by the way. Interesting topic but I confess outside my knowledge.

 

[Dana Riddle]

@Dana Riddle thank you for this! I am wondering this myself. I recently purchased a Seneye Reef PAR meter and it is giving readings around 1500+ at the top of the rocks and around 500+ at the sand bed. Seems very high. However, I run 4 black boxes at 100% both channels with 2 80w Blue+ T5s. I am getting decent growth and coloring but wondering if I am stunting the growth. I have an acro dominate tank and nothing has bleached as of yet. Do you think it is possible that the PAR meter is correct?

Also, I am curious how do you know when photochemical quenching is happening and photosynthesis has shut down?

Based on experiments I did in Hawaii, shallow tide pool Porites corals were beginning to slow their rates of photosynthesis by mid-morning and would not regain until light intensity began to drop in late afternoon. As for your observations, it is difficult to tell. Branching corals (such as Acroporas) can self-shade when heavily branched. It is likely the top of the branch is photoinhibited, while the shaded side is not. I have a Seneye device and could compare measurements. If I ever enough time!

 

[User1]

If I ever enough time!

You need an apprentice

 

[oreo54]

I see micromol/m2/sec as a formula but not sure what it is or if it is something at hobbyists level person can calculate. Or

Thanks by the way. Interesting topic but I confess outside my knowledge.

Actually that's PAR or more correctly PPFD which all these quantum meters measure..

The meter approximates radiation between 400 and 700 nanometers (PAR) as µmol m-2 s-1.

100 "PAR" is 100 PPFD or 100 µmol /meter squared /second

Technically PAR is unitless and just a description.
Photosynthetically useable radiation (PAR) is defined as the energy band between 400-700nm (arguably different nowadays).

 

[Bpb]

What an awesome thread. I personally prefer a brighter white tank, but don’t want to over illuminate. For an acropora dominant system what are the thoughts of running a program of 200-300 par with only 420-450-480nm channels running for an 8 hour photoperiod, and the final 4 hours in the evening when I am home from work and enjoying the tank to run a higher 400-500 par chunk at lower kelvin to help produce some more colorful protective pigments? I’m opposite of many modern reefers. I want my blues doing the heavy lifting when I’m not home and viewing the tank. When I’m here to enjoy it, I prefer 10,000-14,000k

 

[Dana Riddle]

You need an apprentice

The lab work is often boring and tedious and it takes a lot of discipline to perform. The pay off is when data screams 'eureka'!

 

[Dana Riddle]

You probably have one, or I missed it (probably the case), but is there an article that guilds a hobbyist say with a seneye to calculate this? I see micromol/m2/sec as a formula but not sure what it is or if it is something at hobbyists level person can calculate. Or if it is even worth knowing.

Thanks by the way. Interesting topic but I confess outside my knowledge.

Post #13 in this thread has a link to DLI. If your lights are simply on an on/off schedule then DLI is easy to calculate. But ramping makes it difficult unless you have a data logger for light intensity. The PMK (PAR sensor) for the Neptune Apex device can gather data for DLI calcs, so can many of the Apogee PAR meters.

 

[Dana Riddle]

What an awesome thread. I personally prefer a brighter white tank, but don’t want to over illuminate. For an acropora dominant system what are the thoughts of running a program of 200-300 par with only 420-450-480nm channels running for an 8 hour photoperiod, and the final 4 hours in the evening when I am home from work and enjoying the tank to run a higher 400-500 par chunk at lower kelvin to help produce some more colorful protective pigments? I’m opposite of many modern reefers. I want my blues doing the heavy lifting when I’m not home and viewing the tank. When I’m here to enjoy it, I prefer 10,000-14,000k

Sounds like a good plan to me. I too prefer the crisp blue/white look of 14000K (especially when showcasing corals' non-fluorescent chromoproteins).

 

[Dana Riddle]

Actually that's PAR or more correctly PPFD which all these quantum meters measure..

100 "PAR" is 100 PPFD or 100 µmol /meter squared /second

Technically PAR is unitless and just a description.
Photosynthetically useable radiation (PAR) is defined as the energy band between 400-700nm (arguably different nowadays).

PAR and PPFD have become interchangeable terms in the hobby. Yes, you are correct we can get a little sloppy with the terminology.

 

[User1]

Post #13 in this thread has a link to DLI. If your lights are simply on an on/off schedule then DLI is easy to calculate. But ramping makes it difficult unless you have a data logger for light intensity. The PMK (PAR sensor) for the Neptune Apex device can gather data for DLI calcs, so can many of the Apogee PAR meters.

Thanks. I do actually ramp up, and down starting at 0500 and ending at 2200. However, I'll check just to get a number and measure at the peak just to see. Curiosity more or less and to see if I can even do it.

Supposed to be 108 tomorrow so might as well putz around the house.

 

[Dana Riddle]

@Dana Riddle thank you for this! I am wondering this myself. I recently purchased a Seneye Reef PAR meter and it is giving readings around 1500+ at the top of the rocks and around 500+ at the sand bed. Seems very high. However, I run 4 black boxes at 100% both channels with 2 80w Blue+ T5s. I am getting decent growth and coloring but wondering if I am stunting the growth. I have an acro dominate tank and nothing has bleached as of yet. Do you think it is possible that the PAR meter is correct?

Also, I am curious how do you know when photochemical quenching is happening and photosynthesis has shut down?

Measurements of how electrons flow - or don't flow - in the photosynthetic process requires a specialized device called a fluorometer. This instrument can measure chlorophyll fluorescence of Photosystem II and determine which pathway collected light energy is using. Here's a link to the PAM fluorometer (one of two) I have in my lab. A superb instrument:

Walz - Germany

WALZ - one of the worlds top producers of highly sophisticated photosynthesis measuring systems.

walz.com

 

[Dana Riddle]

Thanks. I do actually ramp up, and down starting at 0500 and ending at 2200. However, I'll check just to get a number and measure at the peak just to see. Curiosity more or less and to see if I can even do it.

Supposed to be 108 tomorrow so might as well putz around the house.

To get a decent DLI, you would take measurements hourly and calculate the DLI for each period and then do the math. Gosh, 108. Hope it's a dry heat. It's been mid-90's here with high (80%) humidity. Brutal.

 

[User1]

To get a decent DLI, you would take measurements hourly and calculate the DLI for each period and then do the math. Gosh, 108. Hope it's a dry heat. It's been mid-90's here with high (80%) humidity. Brutal.

Thanks for that tip.

Yes, a dry heat. Northern California so there is that at least I do not enjoy the double whammy with heat and humidity. I had four years of that living in Okinawa (beautiful place) so can relate though.

I'm really not sure where this heat wave came from but the next week or so supposed to be in those ball parks. We'll see.

 

[oreo54]

PAR and PPFD have become interchangeable terms in the hobby. Yes, you are correct we can get a little sloppy with the terminology.

Yea even Purdue does it..

https://www.extension.purdue.edu/extmedia/HO/HO-238-W.pdf

For those w/ a "PAR" meter see pg 4. Just skip the foot candles thing and use "par" reading every hour (smaller the interval the more accurate it is but no need to go all Calculus-y

For example, you have 24 hourly (PAR) readings: 0 + 0 + 0 + 0 + 0 + 5 + 12 + 21 + 40 + 43 + 159 + 399 + 302 + 461 + 610 + 819 + 567 + 434 + 327 + 264 + 126 + 15 + 4 + 0 = 4,408 (PAR) ÷ 24 hours = 184 (PAR) hour

 

[anth]

I was reading a post a few weeks ago about a person that was running 2 photo periods a day, higher par at a short duration. Would this double the daily growth?

 

[Dana Riddle]

I was reading a post a few weeks ago about a person that was running 2 photo periods a day, higher par at a short duration. Would this double the daily growth?

Depends. If we equate rate of photosynthesis to coral growth, then the amount of light matters. If the 'higher PAR at short duration' does not exceed the point where photosynthesis is inhibited, then coral growth should be good. If the amount of light causes dynamic photoinhibition - or worse, chronic photoinhibition, then growth might be reduced, and in worse case the coral could bleach. In hort, I don't think there is much reason to deviate from a 'natural' 12-hour photoperiod. In best case, the light intensity in this photoperiod would be just at the photosaturation point. Now, if we're discussing coloration, that's another matter altogether.

 

[oreo54]

Depends. If we equate rate of photosynthesis to coral growth, then the amount of light matters. If the 'higher PAR at short duration' does not exceed the point where photosynthesis is inhibited, then coral growth should be good. If the amount of light causes dynamic photoinhibition - or worse, chronic photoinhibition, then growth might be reduced, and in worse case the coral could bleach. In hort, I don't think there is much reason to deviate from a 'natural' 12-hour photoperiod. In best case, the light intensity in this photoperiod would be just at the photosaturation point. Now, if we're discussing coloration, that's another matter altogether.

One "possible" exception and may be mildly related to corals.
A punctated photoperiod (siesta) for freshwater plants is "assumed" to allow CO2 levels to rebuild after depletion by plants.
This is believed to give an advantage over algae.
I have no idea if it's valid or not..

W/ corals .. food/pH/CO2/enzyme level shifts.. ????
Food for thought...

I wouldn't assume 2x growth or anything like that though...

 

[Dana Riddle]

One "possible" exception and may be mildly related to corals.
A punctated photoperiod (siesta) for freshwater plants is "assumed" to allow CO2 levels to rebuild after depletion by plants.
This is believed to give an advantage over algae.
I have no idea if it's valid or not..

W/ corals .. food/pH/CO2/enzyme level shifts.. ????
Food for thought...

I wouldn't assume 2x growth or anything like that though...

Carbonate levels in ocean water affect the availability of CO2 to corals. Instead, the enzyme carbonic anhydrase within corals converts carbonate to CO2 which becomes the carbon source for photosynthesis.

 

[oreo54]

Carbonate levels in ocean water affect the availability of CO2 to corals. Instead, the enzyme carbonic anhydrase within corals converts carbonate to CO2 which becomes the carbon source for photosynthesis.

I was really thinking about alternates in corals not CO2 per se.
There are a lot of assembly lines in organisms that MAY benefit from pauses.

ALL mere speculation.

Back to the fw thing some speculate higher plants can "restart" photosynthesis faster than algae giving them a competitive advantage in start stop patterns. More speculation but has a fair following.
Could just be related to photosaturation
moreso than CO2 recharge.
since it can occur at much lower levels.
Need to check this a bit from those running seistas. No matter

Also not limiting this to photosynthesis alone.

Like I said, food for thought.
I believe this has been discussed before but sort of ruled out for corals though not sure it's totally debunked....?????

Siestas that is, but not related to CO2.